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Introduction. Purely chondral injuries of the knee are relatively rare, and no consensus exists on the appropriate treatment in such cases. We describe two adolescent patients with chondral injury of the knee who were successfully treated by osteochondral peg fixation. Patients, Concerns, and Clinical Findings. In case 1, a 14-year-old boy presented with complaints of right knee pain after landing on his leg while playing basketball. Radiography and computerized tomography revealed no abnormalities. However, magnetic resonance imaging revealed a chondral defect in his lateral femoral condyle and a loose chondral fragment measuring 6.5 cm2. In case 2, a 12-year-old boy presented with complaints of left knee pain after a rotational injury while playing baseball. Similar to case 1, magnetic resonance imaging revealed a chondral defect in his lateral femoral condyle and a loose chondral fragment measuring 3.0 cm2. Primary Diagnosis, Interventions, and Outcomes. The two patients were treated by surgical fixation using osteochondral pegs, which were harvested from the femoral condyle. After a year, postoperative computerized tomography and magnetic resonance imaging showed union of the chondral fragment with the osteochondral pegs and surrounding tissue. In both cases, the Lysholm score was 100 points at the final follow-up more than 2 years after surgery. Conclusion. The findings reported herein suggest that osteochondral peg fixation is a feasible treatment option for chondral injury of the knee, with satisfactory outcomes.

Ray-summation (raysum) images reconstructed from computed tomography (CT) volume data resemble digital radiography (DR) images. Therefore, they have a potential to be used instead of DR images.The aim of this study was to compare the physical image quality evaluated by signal-difference-to-noise ratio (SDNR) and clinical usefulness between raysum and DR images. We employed an oval water phantom simulating adult abdomen for image quality measurement. Raysum images were reconstructed from CT volume data using an assumed x-ray quality of 70 keV. DR images were obtained using an indirect-type flat panel detector system. The normalized noise-power spectrum (NNPS) for various same dose indices (DR: entrance surface dose, CT: CT dose index volume) were measured from raysum and DR images. SDNRs were calculated from the results of NNPSs, modulation transfer function (MTF), and cartilage material contrast. Five experienced observers visually compared each pair of a clinical raysum image and a DR image for nine clinical cases (head, finger, pelvis, and foot). MTF of raysum was significantly lower than that of DR. SDNRs of DR were superior to those of raysum for each dose index, by an average factor of 1.24. For head and pelvis images, raysum images were comparable or a little superior compared with the DR images, because the radiation doses of raysum was much higher than those of DR. For finger and foot cases, the raysum images were inferior to DR images due to its lower resolution. Our results indicated a limited clinical usefulness of raysum compared with DR., 出版者照会後に全文公開

The purpose of this study was to address image lag in target tracking and its influence on the accuracy of target tracking. Fluoroscopic images were obtained using a direct type of dynamic flat-panel detector (FPD) . Image lag properties, modulation transfer function (MTF) , and profile curves were measured. Digital phantoms of metal sphere with and without blurred edge due to image lag were simulated using the results, respectively, and then superimposed on breathing chest radiographs of a patient. The moving target with and without image lag was traced using a template-matching technique. In the results, the image lag for the first frame after X-ray cutoff was 2.0% and decreased to less than 0.1% in the fifth frame. In the measurement of profile curves on the edges of tungsten material plates, the effect of image lag was seen as blurred edges of the plate. The blurred edges of the plate were also indicated as reduction of MTF. However, the target could be traced without tracking error. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation.

Reference lines of brain computed tomography (CT) is orbitomeatal (OM) line that runs through the external canthus and the center of the external auditory meatus. However, because it is difficult to identify OM line on the scout image which is 2-dimensional X-ray image, OM line is usually set by radiological technologists subjectively. The purpose of our study is to propose a method which detects the scan angle and the scan range used on the scout images automatically. The algorithm in our proposed method is based on a two-dimensional post-processing that is the method of Hough transformation conversion for detecting the scan angle and the Cross-correlation technique for the scan range. Our proposed method was tested using the scout images of 30 clinical patients' data by visual evaluation of four radiological technologists. Four radiological technologists evaluated the results of the clinical cases and 28 cases (93%) of CT examinations with using our method were acceptable. We confirmed it has the potential to improve the consistency in scan planning of brain CT, because the proposed method detects almost accurately the scan angle and the scan range in clinical cases. In conclusion, it is possible to obtain reproducible slice level images.

A technique called phase contrast mammography (PCM) has only recently been applied in clinical examination. In this application, PCM images are acquired at a 1.75× magnification using an x-ray tube for clinical use, and then reduced to the real size of the object by image processing. The images showed enhanced object edges; reportedly, this enhancement occurred because of the refraction of x rays through a cylindrical object. The authors measured the physical image characteristics of PCM to compare the image characteristics of PCM with those of conventional mammography. More specifically, they measured the object-edge-response characteristics and the noise characteristics in the spatial frequency domain. The results revealed that the edge-response characteristics of PCM outperformed those of conventional mammography. In addition, the characteristics changed with the object-placement conditions and the object shapes. The noise characteristics of PCM were better than those of conventional mammography. Subsequently, to verify why object edges were enhanced in PCM images, the authors simulated image profiles that would be obtained if the x rays were refracted and totally reflected by using not only a cylindrical substance but also a planar substance as the object. So, they confirmed that the object edges in PCM images were enhanced because x rays were refracted irrespective of the object shapes. Further, they found that the edge enhancements depended on the object shapes and positions. It was also proposed that the larger magnification than 1.75 in the commercialized system might be more suitable for PCM. Finally, the authors investigated phase-contrast effects to breast tissues by the simulation and demonstrated that PCM would be helpful in the diagnoses of mammography.

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Computer Assisted Radiology and Surgery 24th International Congress and Exhibition

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There is a concern that image lag may reduce accuracy of real-time target tracking in radiotherapy. This study was performed to investigate influence of image lag on the accuracy of target tracking in radiotherapy. Fluoroscopic images were obtained using a direct type of dynamic flat-panel detector (FPD) system under conditions of target tracking during radiotherapy. The images continued to be read out after X-irradiations and cutoff, and image lag properties in the system were then determined. Subsequently, a tungsten materials plate with a precision edge was mounted on to a motor control device, which provided a constant velocity. The plate was moved into the center of the detector at movement rate of 10 and 20 mm/s, covering lung tumor movement of normal breathing, and MTF and profile curves were measured on the edges covering and uncovering the detector. A lung tumor with blurred edge due to image lag was simulated using the results and then superimposed on breathing chest radiographs of a patient. The moving target with and without image lag was traced using a template-matching technique. In the results, the target could be traced within a margin for error in external radiotherapy. The results indicated that there was no effect of image lag on target tracking in usual breathing speed in a radiotherapy situation. Further studies are required to investigate influence by the other factors, such as exposure dose, target size and shape, imaging rate, and thickness of a patients body.